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Date:   Wed, 12 Dec 2018 01:45:03 -0800
Message-ID: <000000000000665f2e057cd00db6@google.com>
Subject: KASAN: use-after-free Read in handle_userfault (2)
From:   syzbot <syzbot+cbc64b24b2b2d54c07a9@syzkaller.appspotmail.com>
To:     linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk
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Sender: linux-kernel-owner@vger.kernel.org
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Hello,

syzbot found the following crash on:

HEAD commit:    14cf8c1d5b90 Add linux-next specific files for 20181210
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=133296db400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c9133d0a4284c012
dashboard link: https://syzkaller.appspot.com/bug?extid=cbc64b24b2b2d54c07a9
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+cbc64b24b2b2d54c07a9@syzkaller.appspotmail.com

RDX: 00000000000003ff RSI: 0000000020012fe0 RDI: 00007f5dbe489850
RBP: 000000000072bf00 R08: 00000000000003ff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f5dbe48a6d4
R13: 00000000004c578a R14: 00000000004d9d90 R15: 00000000ffffffff
==================================================================
BUG: KASAN: use-after-free in __list_del_entry_valid+0xf1/0x100  
lib/list_debug.c:51
CPU: 1 PID: 20306 Comm: syz-executor2 Not tainted 4.20.0-rc6-next-20181210+  
#164
Read of size 8 at addr ffff8881c5e72bb0 by task kworker/0:1/12
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011

Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x244/0x39d lib/dump_stack.c:113
  handle_userfault.cold.30+0x47/0x62 fs/userfaultfd.c:431
  do_anonymous_page mm/memory.c:2938 [inline]
  handle_pte_fault mm/memory.c:3780 [inline]
  __handle_mm_fault+0x4d26/0x5b70 mm/memory.c:3906
  handle_mm_fault+0x54f/0xc70 mm/memory.c:3943
  do_user_addr_fault arch/x86/mm/fault.c:1475 [inline]
  __do_page_fault+0x5f6/0xd70 arch/x86/mm/fault.c:1541
  do_page_fault+0xf2/0x7e0 arch/x86/mm/fault.c:1572
  page_fault+0x1e/0x30 arch/x86/entry/entry_64.S:1143
RIP: 0033:0x4510a0
Code: 0f 84 c4 0f 00 00 48 89 f1 48 89 f8 48 83 e1 3f 48 83 f9 20 0f 86 7b  
02 00 00 48 83 e6 f0 48 83 e1 0f 66 0f ef c0 66 0f ef c9 <66> 0f 74 0e 66  
0f d7 d1 48 d3 ea 49 c7 c2 11 00 00 00 49 29 ca 4d
RSP: 002b:00007fab1fbba7a8 EFLAGS: 00010202
RAX: 00007fab1fbba850 RBX: 0000000000000003 RCX: 000000000000000e
RDX: 00000000000003ff RSI: 0000000020012fe0 RDI: 00007fab1fbba850
RBP: 000000000072bf00 R08: 00000000000003ff R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fab1fbbb6d4
R13: 00000000004c578a R14: 00000000004d9d90 R15: 00000000ffffffff
CPU: 0 PID: 12 Comm: kworker/0:1 Not tainted 4.20.0-rc6-next-20181210+ #164
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: events_power_efficient neigh_periodic_work
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x244/0x39d lib/dump_stack.c:113
  print_address_description.cold.4+0x9/0x1ff mm/kasan/report.c:187
  kasan_report.cold.5+0x1b/0x39 mm/kasan/report.c:317
  __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:135
  __list_del_entry_valid+0xf1/0x100 lib/list_debug.c:51
  __list_del_entry include/linux/list.h:117 [inline]
  list_del_init include/linux/list.h:159 [inline]
  neigh_mark_dead+0x13b/0x410 net/core/neighbour.c:125
  neigh_periodic_work+0x89a/0xc30 net/core/neighbour.c:905
  process_one_work+0xc90/0x1c40 kernel/workqueue.c:2153
  worker_thread+0x17f/0x1390 kernel/workqueue.c:2296
  kthread+0x35a/0x440 kernel/kthread.c:246
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

Allocated by task 8166:
  save_stack+0x43/0xd0 mm/kasan/common.c:73
  set_track mm/kasan/common.c:85 [inline]
  kasan_kmalloc+0xcb/0xd0 mm/kasan/common.c:482
  __do_kmalloc_node mm/slab.c:3671 [inline]
  __kmalloc_node_track_caller+0x4d/0x70 mm/slab.c:3685
  __kmalloc_reserve.isra.38+0x41/0xe0 net/core/skbuff.c:137
  __alloc_skb+0x155/0x770 net/core/skbuff.c:205
  alloc_skb include/linux/skbuff.h:1008 [inline]
  netlink_alloc_large_skb net/netlink/af_netlink.c:1182 [inline]
  netlink_sendmsg+0xb29/0xfc0 net/netlink/af_netlink.c:1892
  sock_sendmsg_nosec net/socket.c:622 [inline]
  sock_sendmsg+0xd5/0x120 net/socket.c:632
  ___sys_sendmsg+0x7fd/0x930 net/socket.c:2117
  __sys_sendmsg+0x11d/0x280 net/socket.c:2155
  __do_sys_sendmsg net/socket.c:2164 [inline]
  __se_sys_sendmsg net/socket.c:2162 [inline]
  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8166:
  save_stack+0x43/0xd0 mm/kasan/common.c:73
  set_track mm/kasan/common.c:85 [inline]
  __kasan_slab_free+0x102/0x150 mm/kasan/common.c:444
  kasan_slab_free+0xe/0x10 mm/kasan/common.c:452
  __cache_free mm/slab.c:3485 [inline]
  kfree+0xcf/0x230 mm/slab.c:3804
  skb_free_head+0x99/0xc0 net/core/skbuff.c:550
  skb_release_data+0x70c/0x9a0 net/core/skbuff.c:570
  skb_release_all+0x4a/0x60 net/core/skbuff.c:627
  __kfree_skb net/core/skbuff.c:641 [inline]
  consume_skb+0x1ae/0x570 net/core/skbuff.c:701
  netlink_unicast_kernel net/netlink/af_netlink.c:1311 [inline]
  netlink_unicast+0x5ad/0x760 net/netlink/af_netlink.c:1336
  netlink_sendmsg+0xa18/0xfc0 net/netlink/af_netlink.c:1917
  sock_sendmsg_nosec net/socket.c:622 [inline]
  sock_sendmsg+0xd5/0x120 net/socket.c:632
  ___sys_sendmsg+0x7fd/0x930 net/socket.c:2117
  __sys_sendmsg+0x11d/0x280 net/socket.c:2155
  __do_sys_sendmsg net/socket.c:2164 [inline]
  __se_sys_sendmsg net/socket.c:2162 [inline]
  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2162
  do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
  entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8881c5e72940
  which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 624 bytes inside of
  1024-byte region [ffff8881c5e72940, ffff8881c5e72d40)
The buggy address belongs to the page:
page:ffffea0007179c80 count:1 mapcount:0 mapping:ffff8881da800ac0  
index:0xffff8881c5e72dc0 compound_mapcount: 0
flags: 0x2fffc0000010200(slab|head)
raw: 02fffc0000010200 ffffea00072cf188 ffffea00075d0c08 ffff8881da800ac0
raw: ffff8881c5e72dc0 ffff8881c5e72040 0000000100000005 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
  ffff8881c5e72a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8881c5e72b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff8881c5e72b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                      ^
  ffff8881c5e72c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
  ffff8881c5e72c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
kobject: 'loop5' (00000000a3f9d928): kobject_uevent_env


---
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